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A051683
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Triangle read by rows: a(n,k)=n!*k.
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11
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1, 2, 4, 6, 12, 18, 24, 48, 72, 96, 120, 240, 360, 480, 600, 720, 1440, 2160, 2880, 3600, 4320, 5040, 10080, 15120, 20160, 25200, 30240, 35280, 40320, 80640, 120960, 161280, 201600, 241920, 282240, 322560, 362880, 725760, 1088640, 1451520
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OFFSET
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1,2
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COMMENTS
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Numbers with only one non-zero digit when written in base factorial. - Franklin T. Adams-Watters, Nov 28 2011.
In other words, numbers n such that A034968(n) = A099563(n). - Antti Karttunen, Jul 02 2013
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LINKS
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Reinhard Zumkeller, Rows n=1..150 of triangle, flattened
Tilman Piesk, Arrays of permutations
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FORMULA
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a(n) = A000142(A002024(n)) * A002260(n) = A002024(n)! * A002260(n). - Antti Karttunen, Jul 02 2013
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EXAMPLE
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Table begins
1
2 4
6 12 18
24 48 72 96 ...
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MATHEMATICA
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a[n_, k_] := n!*k; Flatten[Table[a[n, k], {n, 9}, {k, n}]] (* Jean-François Alcover, Apr 22 2011 *)
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PROG
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(Haskell)
a051683 n k = a051683_tabl !! (n-1) !! (k-1)
a051683_row n = a051683_tabl !! (n-1)
a051683_tabl = map fst $ iterate f ([1], 2) where
f (row, n) = (row' ++ [head row' + last row'], n + 1) where
row' = map (* n) row
-- Reinhard Zumkeller, Mar 09 2012
(Scheme): (define (A051683 n) (* (A000142 (A002024 n)) (A002260 n))) -- Antti Karttunen, Jul 02 2013
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CROSSREFS
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Cf. A000142, row sums give A001286(n+1).
Cf. A007623.
Cf. A200748.
Cf. A162608.
Sequence in context: A060735 A181416 A225566 * A215821 A192096 A181740
Adjacent sequences: A051680 A051681 A051682 * A051684 A051685 A051686
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KEYWORD
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easy,nice,nonn,tabl
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AUTHOR
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Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de)
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STATUS
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approved
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